The Higgsy Higgsy Boson

A few years ago, when my children were infants, I used to amuse myself (and, I hoped, pacify them) by changing the words to nursery rhymes and other children's songs. I made them all about physics and astronomy. "Twinkle twinkle little star" was a gimme; the Muppets' "Rainbow Connection" became a song about Pluto ("Why are there suddenly only eight planets?"). My favorite went to the tune of the Itsy Bitsy Spider: "The Higgsy Higgsy boson was in the LHC..."

As my children (now kindergarteners) can tell you, "LHC" stands for "Large Hadron Collider," the enormous particle accelerator at the CERN laboratory near Geneva. And the Higgsy Higgsy boson? Physicists who are not straining to fit a song's meter know it better as the "Higgs boson," named in honor of British physicist Peter Higgs. (A "boson" is a kind of particle; other familiar bosons include photons, quantum particles of light.)

About fifty years ago, Higgs and several colleagues hypothesized that a new type of elementary particle with specific properties should exist. In fact, they suggested that the new particle should be so ubiquitous that we are all bathed in a sea of them all the time, without even noticing them. The idea behind the Higgs particle was to give other particles their mass--to account for why some elementary particles trudge along as heavyweights or welterweights (on the subatomic scale) rather than zooming around at the speed of light.

You can think of Higgs particles as invisible soccer balls, constantly being kicked back and forth between the particles that we observe. Rather than zipping straight across the field at the speed of light, the particles that are "kicking" or interacting with the Higgs particles follow zigzag paths, and hence take longer to move from one place to another. We interpret their slower rate as a sign that they are lugging a heavy load, that is, that they have some mass.

The Higgs particle has been on my mind for a long time. Back in college my friends used to tease me for my Ahab-like obsession with the funny-sounding particle. (Naturally I assumed that they were jealous that I got to spend my time daydreaming about the origin of mass.) My first scientific article, written almost twenty years ago, focused on the hunt for the Higgs: one more insignificant paper piled on the mountain that had already accumulated on the topic. More recently, I have been working with colleagues to understand what roles Higgs particles might have played in the very early universe, mere moments after the big bang--and whether the quantum jitter of Higgs particles back then might have left observable signals in the skies today.

Indeed, finding the Higgs particle has been at or near the top of particle physicists' wish list for decades. Although there have been tantalizing hints of the Higgs in previous experiments--including as recently as last summer--none of those results panned out.

That's why I sat mesmerized a few weeks ago, watching the live-streaming feed of a press conference at CERN. The video was choppy, cutting out every few seconds. Being an optimist, I chose to interpret the poor signal quality as due to heavy internet traffic: wasn't everybody trying to watch the teleconference at 8am Eastern time?

At the press conference, physicists from two independent groups presented updates on their searches for the Higgs particle at the LHC. They necessarily stopped short of claiming successful detection--that will require considerably more data to rule out the possibility of statistical flukes, background noise from non-Higgs processes that could mimic a genuine Higgs signal. But what they presented was the most compelling evidence to date that the Higgs boson might actually exist, pretty much right where theorists hoped it would be.

There are many reasons to be cautious before jumping to premature conclusions. For my money, you can't do better than physicist Matthew Strassler's blog for a smart, accessible guide to the finer points involved.

For all that, I still get a tingly feeling when I think back to that press conference and the possibilities on display. Searching for the Higgs particle has occupied physicists for half a century. And yet before my kids finish first grade, we very well could know whether the Higgs particle exists, at least in the form we most expect to find. And that would be worth singing about.